The concept of battery parts made of lead that have a threaded fastener such as a bolt or a nut embedded in the battery part are known in the art. Typically, the battery terminals are made from lead, which is a good electrical conductor but relatively soft. In order to support a threaded connection to the lead battery terminal a fastener made of a harder material is embedded within the battery terminal. In one embodiment a nut having an internal thread is embedded within the terminal so that a male fastener can threadingly engage the threads on the nut to form a good electrical connection therebetween. In another embodiment a stud bolt having a head on one end and a male thread on the other end is partially embedded in the battery terminal with the male threads in a condition to receive a female fastener. In both cases battery cables or the like can be firmly secured to the battery terminal using the threads on the embedded fastener.
One of the difficulties with the use of fasteners made of harder material such as steel is that while the harder fasteners provide threads that retain their integrity and thus can be used to tightly secure a battery cable thereto, the fasteners can be accidentally twisted free of the supporting lead battery terminal. Typically, a fasteners such as a bolt or nut is made from a non-lead material such as stainless steel and includes a hexagonal shaped head or the like that mechanically engages the lead in the battery terminal similar to a wrench engaging the flats on the sides of a fastener. The fastener, which is formed separate from the battery terminal is mechanically secured in the terminal by either cold forming the lead around the fastener or pouring molten lead into a mold surrounding the fastener. The lead is allowed to cool and solidity around the fastener exterior sides to mechanically lock the fastener to the battery terminal.
By mechanically locking the embedded fasteners to the battery terminal one inhibits the fastener from rotating when an external member is secured to the fastener similar to the manner a wrench engages the flats on a fastener to prevent rotation thereof. Thus the mechanical locking provides a torque resistance that maintains the fastener in a non-rotatable condition in the battery terminal. Although mechanical engagement between the embedded fastener prevents the fastener from rotating in the battery terminal, if the external fastener is accidentally over torqued the excess torque on the embedded fastener can deform the soft lead in the battery terminal, which allows the embedded fastener to rotate within the terminal. If the fastener is free to rotate within the terminal it can result in a person having to replace the entire battery.
The present invention provides a method of enhancing the torque resistance of an embedding fastener, which is normally retained solely by mechanical engagement in a battery terminal, by the discovery that interposing a layer of an adhereable material between the fastener and the battery part provides an embedded fastener with enhanced torque resistance.